are modulus of elasticity in shear, yield shear strength,ultimate shear strength,andmodulus of rupture in shear

and ductility

The torsion test generates the "torque versus angle" diagramthatlooks

very similar to a"stress versus strain" curvein

a tensile

test.

They are not the same howeverthey areanalogous to properties that can be

determined during a tensile test

3.EQUIPMENT & MATERIALS

3.1

Equipment

Torsion Tester

Machine

3.2

Materials

Aluminum & Mild Steel

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Fig. 1Torsion test machine

3.

TORSION TEST

The most notable test that demonstrates the effects of shearing forces and resultingstresses is the torsion test of a solid circular bar or rod. As a matter of fact, this testgenerates a state of pure shear stress in the torsional loaded rod. Such a test is used toascertain all the major shear properties of metal materials, i.e., the ultimate shear stress, theyield shear stress and the modulus of rigidity or shear modulus.

Figure 1

The applied torque (T)asshown inFigure 1,to the specimen and resulting deformation(angle of twist,) are measured during the torsion test. Theseresults

are converted to shearstress () and shear strain() by the following respective equations:

(1)

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(2)

wherec

is the radius of the solid circular rod,Lo

is the length over which the relative angle oftwist is measured (this angle must be in radians) andJ

is the polar moment of inertia definedas follows:

(3)

The shear modulus of elasticity is defined as the linear slope, of the shear stress-shearstrain relation, between zero shear stress and the proportional limit shear stress (definedbelow), i.e.,

(4)

This equation clearly states that the shear modulus, like Young’s modulus, is only valid forthe linear elastic range of the material

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4.PROCEDURE

The setup procedure is given as follow:

4.1

Loosen the four screws on the movable steel plate. Move the movable steel plateto behind.

4.2

Select the desired test specimen and identifythe material. Record it into a Table

1.

4.3

Measurediameter of the test specimen using appropriate tools. Repeat themeasurement few times and take the average reading.

4.4

Draw,

with a pencil

or marker, a line

on the straight section of the specimen sothat the line

is

90 mm. This will be the gage length,Lo.

4.5

Fix the hexagonal sockets to bothsides

of the torque shafts.

4.6

Insert the test specimen to the one of the hexagonal socket. Follow theinstruction givenby Teaching Engineer.

4.7

Push the movable steel plate so that the test specimen can be inserted into thesecond hexagonal socket. If the test specimen could not fit into the secondsocket, slowly turn the motor shaft adjustor until the specimen is inserted to thesocket.

4.8

Tighten the four screws provided.

4.9

Switch ON the MCB/ELCB and the ON/OFF switch on the control box.

4.10

Tare the torque meter and the counter to zero reading. Make sure the maximumand minimum torque readingis tare

as well.

4.11

Press the ‘RUN’ soft button on the frequency inverter. Slowly increase thefrequency and keep an eye on the torque reading.

4.12

For

every 0.5Nm of torque increment,record downs

the value on dial indicator.Repeat this step until maximum torque reached (where the torquevalue nolonger increases).

4.13

Once the maximum torque reached or plastic region reached, press the stop softbutton on the frequency inverter.

4.14

Repeat procedure for each specimen.

4.15

Turn main switch ‘OFF’.

5.ANALYSIS

5.1.

Make a table giving the specimen, the original dimensions and the finaldimensions.This will be Table1.

5.2.

Construct ashearstress-shear strain

curve from thetorque-anglecurve

i.

First,make copies of

yourtorque-anglecurve

data and insert it onTable 2.

ii.

Next,construct

thetorque-anglecurves

by utilizing spreadsheetsoftware and name it as Fig. 1.The

torque

is on the y-axis andangle

is on the x-axis.The unit of torque and angle

areN.m

anddeg,

respectively.

iii.

For each point, compute theshearstress

andangle.Useradian

(rad)as the unit forshear strain

andMPa

as the unit forshearstress.Insertthe result on Table 3

iv.

Plot the data points ofshearstress vs.

shear strain

and draw asmooth curve through them and name it as Fig. 2

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5.3.

Using theFig. 2

make the following

calculations (and on the graphs, show howyou made those calculations)

i.

Theshearmodulus.

ii.

Proportional limit

iii.

Ultimate stress

iv.

Maximum elastic displacement (in elastic region)

v.

Maximum shear stress (in elastic region)

5.4.

Make another table

that isTable4

and insert the results properly.

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Name

:

______________________________Date

: ______________

Matrix No

:

______________________________

5.DATA &RESULTS:

TABLE 1

Material Name

OriginalDiameter

Original GageLength

Final GageLength

TABLE2

No

Torque

(N.m)

Angle

(deg)

1

2

3

…

end

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Name

:

______________________________Date

: ______________

Matrix No

:

______________________________

Fig. 1

Fig. 1Torque

vs.Angle

TABLE3

No

Torque

(N.m

)

Angle

(deg

)

ShearStress

( MPa )

Shear Strain

(rad)

1

2

3

…

end

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Name

:

______________________________Date

: ______________

Matrix No

:

______________________________

Fig. 2

Fig. 2(a)ShearStress

vs.Shear Strain

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Name

:

______________________________Date

: ______________

Matrix No

:

______________________________

TABLE4

Parameters

Results

Theshearmodulus

Proportional limit

Ultimate stress

Maximum elasticdisplacement

Maximum shearstress

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Name

:

______________________________Date

: ______________

Matrix No

:

______________________________

6. QUESTIONS

Answer all the questions

6.1 Using your own word, what do you understand aboutTorsion?

6.2. Give three examples

where torsion are applied?

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Name

:

______________________________Date

: ______________

Matrix No

:

______________________________

7.DISCUSSION

(Include a discussion on the result noting trends in measured data, and comparing measurements with theoretical predictions whenpossible.

Include the physical interpretation of the results and graphs, the reasons on deviations of your findings from expected results, yourrecommendations on further experimentation for verifying your results, and your findings.)

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Name

:

______________________________Date

: ______________

Matrix No

:

______________________________

8.CONCLUSION

(Based on data and discussion, make your overall conclusion by referring to experiment objective).

The conclusion for this lab is…

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REFERENCES

R.C. Hibbeler. (2005).

SI 2th.ed.

Mechanics of Materials.Prentice Hall

James M. Gere. (2004).

6th

ed.Mechanics of Materials.Thomson.

David W. A. Rees.(2000).Mechanics of Solids and Structures

Imperial College Press.

Instron Homepage, www.instron.com

APPENDIX

Shear Modulus of Elasticity

Tangent or secant modulus of elasticity of a material subjected to shear loading.Alternate terms are modulus of rigidity and modulus of elasticityin shear. Also, shearmodulus of elasticity usually is equal to

Torsional Modulus of Elasticity.A method fordetermining shear modulus of elasticity of structural materials by means of a twisting testis given in ASTM E-143. A method for determining shear

modulus of structuraladhesives is given in ASTM E-229.

Torsional Modulus of Elasticity

Modulus of

Elasticity

of material subjected to twist loading. It is approximately equal toshear modulus and also is called modulus of rigidity.

Torsional Strength

Measure of the ability of a material to withstand a twisting load. It is theUltimate strengthof a material subjected to torsional loading, and is the maximum torsional stress that amaterial sustains before rupture. Alternate terms are modulus of rupture and shearstrength.